Even though many uses of papers have been replaced by electronic documentations due to concerns of environmental issues, documents still have to be printed on papers under certain circumstances. With the help of machines such as printer, copier, fax machine, scanner, and all-in-one multifunction center, graphics, symbols, texts, and pictures can be printed onto papers for a better visualization and comprehension of the enclosure. A printer, as an instance, usually contains at least one set of the printing mechanism and one set of the paper transporting mechanism. After a paper enters the printer, the paper transporting mechanism passes the paper to the printing mechanism inside the printer to have graphics, symbols, texts, and pictures printed onto the paper; then the paper transporting mechanism outputs the paper from the printer. In order to ensure the paper which enters and exits the printer is flat, paper trays, either fix or movable, are usually included and attached at the paper entrance and exit ends of the printer. If the movable paper trays are used for both input and output paper trays, paper trays can be either folded along the side of the printer or slid into the printer body to allow more spaces for other usage or to have the printer ready to repack into the original box. Nevertheless, using printers with movable paper trays require more setting up/unset up steps. In order to have the printer ready, the user has to either unfold or pull out the paper trays one by one before papers can be fed into it. On the other hand, after using the printer, the movable paper trays need to be either folded or slid in separately before the printer is compact enough to free up spaces for other usage or repack into the original box.